Electrostatic ink jet printing mechanism

ABSTRACT

This patent describes an ink jet printer where ink is ejected from a nozzle chamber by means of the utilisation of the electrostatic attraction between two parallel plates. An electrostatic actuator includes a first planar electrode formed within a bottom and a moveable second planar electrode arranged above the first planar electrode. The second planar electrode is moveable to a pre-firing position adjacent to the first planar electrode, thereby causing a corrugated border portion of the second electrode to concertina. Upon reduction of a potential difference, the corrugated border returns to its quiescent position, thereby causing the ejection of ink from the nozzle chamber. Between the first planar electrode and the second planar electrode is an air gap interconnected to an external atmosphere at a side of the nozzle chamber such that air flows into and out of the gap upon movement of the actuator.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, US patent applications identified by their US patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the US patent applications claim the right ofpriority.

CROSS-REFERENCED U.S. patent application AUSTRALIAN (CLAIMING RIGHT OFPRIORITY PROVISIONAL FROM AUSTRALIAN DOCKET PATENT NO. PROVISIONALAPPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO798809/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO801409/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO799909/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO803009/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO801509/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO798909/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO801809/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO802409/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO850109/112,797 ART30 PO8500 09/112,796 ART31 PO7940 09/113,072 ART28 PO793909/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO798709/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO802009/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO800009/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799009/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO798109/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO802609/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO939409/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO939809/112,792 ART60 PO9399 09/112,791 ART61 PO9400 09/112,790 ART62 PO940109/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO940509/112,749 ART66 PPO959 09/112,784 ART68 PP1397 09/112,783 ART69 PP237009/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 1J12 PO8036 09/112,8181J13 PO8048 09/112,816 1J14 PO8070 09/112,772 IJ15 PO8067 09/112,819IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827IJM04 PO8054 09/112,828 IJM05 PO8065 09/113,111 IJM06 PO8055 09/113,108IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 09/113,089IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774IR18 PP0883 09/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092IR21 PO8006 09/113,100 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062MEMS04 PO8010 09/113,064 MEMS05 PO8011 09/113,082 MEMS06 PO794709/113,081 MEMS07 PO7944 09/113,080 MEMS09 PO7946 09/113,079 MEMS10PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses an Electrostatic Ink Jet Printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques of ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different types. Theutilisation of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al) Piezoelectric ink jet printers are also oneform of commonly utilized ink jet printing device. Piezoelectric systemsare disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) whichutilises a diaphragm mode of operation, by Zolten in U.S. Pat. No.3,683,212 (1970) which discloses a squeeze mode of operation of apiezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972)discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat.No. 4,459,601 discloses a Piezoelectric push mode actuation of the inkjet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses asheer mode type of piezoelectric transducer element. Recently, thermalink jet printing has become an extremely popular form of ink jetprinting. The ink jet printing techniques include those disclosed byEndo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No.4,490,728. Both the aforementioned references disclosed ink jet printingtechniques rely upon the activation of an electrothermal actuator whichresults in the creation of a bubble in a constricted space, such as anozzle, which thereby causes the ejection of ink from an apertureconnected to the confined space onto a relevant print media. Printingdevices utilising the electro-thermal actuator are manufactured bymanufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

The present invention relates to a new form of ink jet printing whereinthe ink is ejected from a nozzle chamber by means of the utilization ofthe electrostatic attraction between two parallel plates.

In accordance with the first aspect of the present invention there isprovided an ink jet nozzle comprising a nozzle chamber having an inkejection port in one wall of the chamber, an ink supply sourceinterconnected to the nozzle chamber, an electrostatic actuatorcomprising a first planar electrode formed within a bottom substrate ofthe nozzle chamber and a moveable second planar electrode arranged abovethe first planar electrode, wherein the second planar electrode ismoveable to a pre-firing position adjacent to said first planarelectrode, upon forming a potential difference across the electrodes,thereby causing a corrugated border portion of the second electrode toconcertina, such that, upon reduction of the potential difference, thecorrugated border returns to its quiescent position and thereby causesthe ejection of ink from the nozzle chamber.

In accordance with the second aspect of the present invention there isprovided an ink jet nozzle comprising a nozzle chamber having an inkejection port in one wall of the chamber, an ink supply sourceinterconnected to the nozzle chamber, an electrostatic actuator to ejectink from the nozzle chamber via the ink ejection port, wherein theelectrostatic actuator comprises a first planar electrode formed withina bottom substrate of the nozzle chamber and a moveable second planarelectrode arranged above the first planar electrode, and the ink jetnozzle arrangement is being formed from the depositing and etching ofmaterial on a single monolithic wafer. Further, there is an air gapbetween the first and second planar electrode which is interconnected toan external atmosphere at a side of the nozzle chamber such that airflows into and out of the gap upon movement of the actuator. Preferablythe surface of the electrodes facing and opposing electrode are coatedwith a material having a low coefficient of friction so as to reduce thepossibilities of stiction. Advantageously this material comprised ofsubstantially polytetrafluoroethylene. The second planar electrodeincludes preferable a layer of stiffening materials for maintaining thestiffness of the second planar electrode which is substantiallycomprised of nitride. The air gap between a first and a second planarelectrode structure is formed by utilization of a sacrificial materiallayer which is etched away to release the second planar electrodestructure.

Further an outer surface of the ink chamber includes a plurality ofetchant holes provided so as to allow a more rapid etching ofsacrificial layers during construction.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings, which:

FIG. 1 is a perspective cross-sectional view of a single ink jet nozzleconstructed in accordance with the preferred embodiment;

FIG. 2 is a close-up perspective cross-sectional view (portion A of FIG.1), of a single ink jet nozzle constructed in accordance with thepreferred embodiment;

FIG. 3 is an exploded perspective view illustrating the construction ofa single ink jet nozzle in accordance with the preferred embodiment;

FIG. 4 provides a legend of the materials indicated in FIGS. 5 to 15;and

FIG. 5 to FIG. 15 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, an ink jet print head is made up of aplurality of nozzle chambers each having an ink ejection port. Ink isejected from the ink ejection port through the utilization of attractionbetween two parallel plates.

Turning initially to FIG. 1, there is illustrated a cross-sectional viewof a single nozzle arrangement 10 as constructed in accordance with thepreferred embodiment. The nozzle arrangement 10 includes a nozzlechamber 11 in which is stored ink to be ejected out of an ink ejectionport 12. The nozzle arrangement 10 can be constructed on the top of asilicon wafer utilizing micro electro-mechanical systems constructiontechniques as will become more apparent hereinafter. The top of thenozzle plate also includes a series of regular spaced etchant holes,e.g. 13 which are provided for efficient sacrificial etching of lowerlayers of the nozzle arrangement 10 during construction. The size of theetchant holes 13 is small enough that surface tension characteristicsinhibit ejection from the holes 13 during operation.

Ink is supplied to the nozzle chamber 11 via an ink supply channel, e.g.15.

Turning now to FIG. 2, there is illustrated a cross-sectional view ofone side of the nozzle arrangement 10. A nozzle arrangement 10 isconstructed on a silicon wafer base 17 on top of which is firstconstructed a standard CMOS two level metal layer 18 which includes therequired drive and control circuitry for each nozzle arrangement. Thelayer 18, which includes two levels of aluminum, includes one level ofaluminum 19 being utilized as a bottom electrode plate. Other portions20 of this layer can comprise nitride passivation. On top of the layer19 there is provided a thin polytetrafluoroethylene (PTFE) layer 21.

Next, an air gap 27 is provided between the top and bottom layers. Thisis followed by a further PTFE layer 28 which forms part of the top plate22. The two PTFE layers 21, 28 are provided so as to reduce possiblestiction effects between the upper and lower plates. Next, a topaluminum electrode layer 30 is provided followed by a nitride layer (notshown) which provides structural integrity to the top electro plate. Thelayers 28-30 are fabricated so as to include a corrugated portion 23which concertinas upon movement of the top plate 22.

By placing a potential difference across the two aluminum layers 19 and30, the top plate 22 is attracted to bottom aluminum layer 19 therebyresulting in a movement of the top plate 22 towards the bottom plate 19.This results in energy being stored in the concertinaed springarrangement 23 in addition to air passing out of the side air holes,e.g. 33 and the ink being sucked into the nozzle chamber as a result ofthe distortion of the meniscus over the ink ejection port 12 (FIG. 1).Subsequently, the potential across the plates is eliminated therebycausing the concertinaed spring portion 23 to rapidly return the plate22 to its rest position. The rapid movement of the plate 22 causes theconsequential ejection of ink from the nozzle chamber via the inkejection port 12 (FIG. 1). Additionally, air flows in via air gap 33underneath the plate 22.

The ink jet nozzles of the preferred embodiment can be formed fromutilization of semiconductor fabrication and MEMS techniques. Turning toFIG. 3, there is illustrated an exploded perspective view of the variouslayers in the final construction of a nozzle arrangement 10. At thelowest layer is the silicon wafer 17 upon which all other processingsteps take place. On top of the silicon layer 17 is the CMOS circuitrylayer 18 which primarily comprises glass. On top of this layer is anitride passivation layer 20 which is primarily utilized to passivateand protect the lower glass layer from any sacrificial process that maybe utilized in the building up of subsequent layers.

Next there is provided the aluminum layer 19 which, in the alternative,can form part of the lower CMOS glass layer 18. This layer 19 forms thebottom plate. Next, two PTFE layers 26, 28 are provided between which islaid down a sacrificial layer, such as glass, which is subsequentlyetched away so as to release the plate 22 (FIG. 2). On top of the PTFElayer 28 is laid down the aluminum layer 30 and a subsequent thickernitride layer (not shown) which provides structural support to the topelectrode stopping it from sagging or deforming. After this comes thetop nitride nozzle chamber layer 35 which forms the rest of the nozzlechamber and ink supply channel. The layer 35 can be formed from thedepositing and etching of a sacrificial layer and then depositing thenitride layer, etching the nozzle and etchant holes utilizing anappropriate mask before etching away the sacrificial material.

Obviously, print heads can be formed from large arrays of nozzlearrangements 10 on a single wafer which is subsequently diced intoseparate print heads. Ink supply can be either from the side of thewafer or through the wafer utilizing deep anisotropic etching systemssuch as high density low pressure plasma etching systems available fromsurface technology systems. Further, the corrugated portion 23 can beformed through the utilisation of a half tone mask process.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer 40, complete a 0.5 micron, onepoly, 2 metal CMOS process 42. This step is shown in FIG. 5. Forclarity, these diagrams may not be to scale, and may not represent across section though any single plane of the nozzle. FIG. 4 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross referenced ink jet configurations. FIG. 4 is akey to representations of various materials in these manufacturingdiagrams, and those of other cross referenced ink jet configurations.

2. Etch the passivation layers 46 to expose the bottom electrode 44,formed of second level metal. This etch is performed using Mask 1. Thisstep is shown in FIG. 6.

3. Deposit 50 nm of PTFE or other highly hydrophobic material.

4. Deposit 0.5 microns of sacrificial material, e.g. polyimide 48.

5. Deposit 0.5 microns of (sacrificial) photosensitive polyimide.

6. Expose and develop the photosensitive polyimide using Mask 2. Thismask is a gray-scale mask which defines the concertina edge 50 of theupper electrode. The result of the etch is a series of triangular ridgesat the circumference of the electrode. This concertina edge is used toconvert tensile stress into bend strain, and thereby allow the upperelectrode to move when a voltage is applied across the electrodes. Thisstep is shown in FIG. 7.

7. Etch the polyimide and passivation layers using Mask 3, which exposesthe contacts for the upper electrode which are formed in second levelmetal.

8. Deposit 0.1 microns of tantalum 52, forming the upper electrode.

9. Deposit 0.5 microns of silicon nitride (Si3N4), which forms themovable membrane of the upper electrode.

10. Etch the nitride and tantalum using Mask 4. This mask defines theupper electrode, as well as the contacts to the upper electrode. Thisstep is shown in FIG. 8.

11. Deposit 12 microns of (sacrificial) photosensitive polyimide 54.

12. Expose and develop the photosensitive polyimide using Mask 5. Aproximity aligner can be used to obtain a large depth of focus, as theline-width for this step is greater than 2 microns, and can be 5 micronsor more. This mask defines the nozzle chamber walls. This step is shownin FIG. 9.

13. Deposit 3 microns of PECVD glass 56. This step is shown in FIG. 10.

14. Etch to a depth of 1 micron using Mask 6. This mask defines thenozzle rim 58. This step is shown in FIG. 11.

15. Etch down to the sacrificial layer 54 using Mask 7. This maskdefines the roof of the nozzle chamber, and the nozzle 60 itself. Thisstep is shown in FIG. 12.

16. Back-etch completely through the silicon wafer 46 (with, forexample, an ASE Advanced Silicon Etcher from Surface Technology Systems)using Mask 8. This mask defines the ink inlets 62 which are etchedthrough the wafer 40. The wafer 40 is also diced by this etch.

17. Back-etch through the CMOS oxide layer through the holes in thewafer 40. This step is shown in FIG. 13.

18. Etch the sacrificial polyimide 54. The nozzle chambers 64 arecleared, a gap is formed between the electrodes and the chips areseparated by this etch. To avoid stiction, a final rinse usingsupercooled carbon dioxide can be used. This step is shown in FIG. 14.

19. Mount the print heads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets at the back of the wafer.

20. Connect the print heads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

21. Hydrophobize the front surface of the print heads.

22. Fill the completed print heads with ink 66 and test them. A fillednozzle is shown in FIG. 15.

The aforementioned half-tone mask process follows fabrication steps asdiscussed in Australian Provisional Patent entitled Image CreationMethod and Apparatus United Sates Patent (IJ16) lodged by the presentapplicant simultaneously herewith, the contents of which are herebyincorporated by cross-reference. It would be appreciated by a personskilled in the art that numerous variations and/or modifications may bemade to the present invention as shown in the preferred embodimentwithout departing from the spirit or scope of the invention as broadlydescribed. The preferred embodiment is, therefore, to be considered inall respects to be illustrative and not restrictive. The presentlydisclosed ink jet printing technology is potentially suited to a widerange of printing systems including: color and monochrome officeprinters, short run digital printers, high speed digital printers,offset press supplemental printers, low cost scanning printers, highspeed pagewidth printers, notebook computers with in-built pagewidthprinters, portable color and monochrome printers, color and monochromecopiers, color and monochrome facsimile machines, combined printer,facsimile and copying machines, label printers, large format plotters,photograph copiers, printers for digital photographic ‘minilabs’, videoprinters, PHOTO CD (PHOTO CD is a registered trade mark of the EastmanKodak Company) printers, portable printers for PDAs, wallpaper printers,indoor sign printers, billboard printers, fabric printers, cameraprinters and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry. Ink is supplied to the back of the printhead byinjection molded plastic ink channels. The molding requires 50 micronfeatures, which can be created using a lithographically micromachinedinsert in a standard injection molding tool. Ink flows through holesetched through the wafer to the nozzle chambers fabricated on the frontsurface of the wafer. The print head printhead is connected to thecamera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

The present invention is useful in the field of digital printing, inparticular, ink jet printing.

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which matches the docket numbers in the table under the headingCross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples Actuator mechanism(applied only to selected ink drops) Thermal An electrothermal Largeforce High power Canon Bubblejet 1979 bubble heater heats the inkgenerated Ink carrier limited Endo et al GB patent to above boilingSimple to water 2,007,162 point, transferring construction Lowefficiency Xerox heater-in-pit significant heat to No moving Hightemperatures 1990 Hawkins et al the aqueous ink. A parts required U.S.Pat. No. 4,899,181 bubble nucleates Fast operation High mechanicalHewlett-Packard TIJ and quickly forms, Small chip area stress 1982Vaught et al expelling the ink. required for Unusual materials U.S. Pat.No. 4,490,728 The efficiency of the actuator required process is low,with Large drive typically less than transistors 0.05% of the Cavitationcauses electrical energy actuator failure being transformed Kogationreduces into kinetic energy bubble formation of the drop. Large printheads are difficult to fabricate Piezo- A piezoelectric Low power Verylarge area Kyser et al electric crystal such as lead consumptionrequired for U.S. Pat. No. 3,946,398 lanthanum zirconate Many ink typesactuator Zoltan (PZT) is electrically can be used Difficult to U.S. Pat.No. 3,683,212 activated, and either Fast operation integrate with 1973Stemme expands, shears, or High efficiency electronics U.S. Pat.No.3,747,120 bends to apply High voltage drive Epson Stylus pressure tothe ink, transistors Tektronix IJ04 ejecting drops. required Fullpagewidth print heads impractical due to actuator size Requireselectrical poling in high field strengths during manufacture Electro- Anelectric field is Low power Low maximum Seiko Epson, Usui et allstrictive used to activate consumption strain (approx. JP 253401/96electrostriction in Many ink types 0.01%) IJ04 relaxor materials can beused Large area such as lead Low thermal required for lanthanumzirconate expansion actuator due to titanate (PLZT) or Electric fieldlow strain lead magnesium strength Response speed is niobate (PMN).required marginal (˜10 μs) (approx. 3.5 High voltage drive V/μm) can betransistors generated required without Full pagewidth difficulty printheads Does not impractical due to require actuator size electricalpoling Ferro- An electric field is Low power Difficult to IJ04 electricused to induce a consumption integrate with phase transition Many inktypes electronics between the can be used Unusual materialsantiferroelectric Fast operation such as PLZSnT (AFE) and (<1 μs) arerequired ferroelectric (FE) Relatively high Actuators require phase.Perovskite longitudinal a large area materials such as tin strainmodified lead High efficiency lanthanum zirconate Electric fieldtitanate (PLZSnT) strength of exhibit large strains around 3 V/μm of upto 1% can be readily associated with the provided AFE to FE phasetransition. Electro- Conductive plates Low power Difficult to IJ02, IJ04static are separated by a consumption operate plates compressible orMany ink types electrostatic fluid dielectric can be used devices in an(usually air). Upon Fast operation aqueous application of a environmentvoltage, the plates The electrostatic attract each other actuator willand displace ink, normally need to causing drop be separated fromejection. The the ink conductive plates Very large area may be in a combor required to honeycomb achieve high structure, or stacked forces toincrease the High voltage drive surface area and transistors may betherefore the force. required Full pagewidth print heads are notcompetitive due to actuator size Electro- A strong electric Low currentHigh voltage 1989 Saito et al, U.S. Pat. No. static pull field isapplied to consumption required 4,799,068 on ink the ink, whereupon LowMay be damaged 1989 Miura et al, electrostatic temperature by sparks dueto U.S. Pat. No. 4,810,954 attraction air breakdown Tone-jet acceleratesthe ink Required field towards the print strength increases medium. asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop Fast operation suchas ejection. Rare earth High efficiency Neodymium Iron magnets with afield Easy extension Boron (NdFeB) strength around 1 from singlerequired. Tesla can be used. nozzles to High local Examples are:pagewidth print currents required Samarium Cobalt heads Copper (SaCo)and metalization magnetic materials should be used for in the neodymiumlong iron boron family electromigration (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K) Soft A solenoid induced Low power Complex IJ01, IJ05,IJ08, magnetic a magnetic field in a consumption fabrication IJ10, IJ12,IJ14, core soft magnetic core Many ink types Materials not IJ15. IJ17electro- or yoke fabricated can be used usually present in magnetic froma ferrous Fast operation a CMOS fab such material such as Highefficiency as NiFe, CoNiFe, electroplated iron Easy extension or CoFeare alloys such as from single required CoNiFe [1], CoFe, nozzles toHigh local or NiFe alloys. pagewidth print currents required Typically,the soft heads Copper magnetic material is metalization in two parts,which should be used for are normally held long apart by a spring.electromigration when the solenoid lifetime and low is actuated, the tworesistivity parts attract, Electroplating is displacing the ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally fromsingle High local to the print head, for nozzles to currents requiredexample with rare pagewidth print Copper earth permanent headsmetalization magnets. should be used for Only the current long carryingwire need electromigration be fabricated on the lifetime and lowprint-head, resistivity simplifying Pigmented inks materials are usuallyrequirements. infeasible Magneto- The actuator uses Many ink types Forceacts as a Fischenbeck, U.S. Pat. No. striction the giant can be usedtwisting motion 4,032,929 magnetostrictive Fast operation Unusualmaterials IJ25 effect of materials Easy extension such as Terfenol- suchas Terfenol-D from single D are required (an alloy of terbium, nozzlesto High local dysprosium and iron pagewidth print currents requireddeveloped at the heads Copper Naval Ordnance High force is metalizationLaboratory, hence available should be used for Ter-Fe-NOL). For longbest efficiency, the electromigration actuator should be lifetime andlow pre-stressed to resistivity approx. 8 MPa. Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EP0771 658 A2 tension pressure is held in a consumption supplementary andrelated reduction nozzle by surface Simple force to effect patentapplications tension. The surface construction drop separation tensionof the ink is No unusual Requires special reduced below the materialsink surfactants bubble threshold, required in Speed may be causing theink to fabrication limited by egress from the High efficiency surfactantnozzle. Easy extension properties from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EP0771 658 A2 reduction locally reduced to construction supplementary andrelated select which drops No unusual force to effect patentapplications are to be ejected. A materials drop separation viscosityreduction required in Requires special can be achieved fabrication inkviscosity electrothermally Easy extension properties with most inks, butfrom single High speed is special inks can be nozzles to difficult toachieve engineered for a pagewidth print Requires 100:1 viscosity headsoscillating ink reduction. pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu et al, generated and without anozzle circuitry EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, EUP drop ejection region. fabrication 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03, IJ09, IJ17, elastic relies uponconsumption operation requires IJ18, IJ19, IJ20, bend differentialthermal Many ink types a thermal insulator IJ21, IJ22, IJ23, actuatorexpansion upon can be used on the hot side IJ24, IJ27, IJ28, Jouleheating is Simple planar Corrosion IJ29, IJ30, IJ31, used. fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for Pigmented inks IJ38, IJ39, IJ40, each actuatormay be infeasible, IJ41 Fast operation as pigment High efficiencyparticles may jam CMOS the bend actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a High forcecan be Requires special IJ09, IJ17, IJ18, thermo- very high generatedmaterial (e.g. IJ20, IJ21, IJ22, elastic coefficient of thermal Threemethods PTFE) IJ23, IJ24, IJ27, actuator expansion (CTE) of PTFERequires a PTFE IJ28, IJ29, IJ30, such as deposition are depositionIJ31, IJ42, IJ43, polytetrafluoroethyl- under process, which is IJ44 ene(PTFE) is used. development: not yet standard in As high CTE chemicalvapor ULSI fabs materials are usually deposition PTFE depositionnon-conductive, a (CVD), spin cannot be heater fabricated coating, andfollowed with from a conductive evaporation high temperature material isPTFE is a (above 350° C.) incorporated. A 50 candidate for processing μmlong PTFE bend low dielectric Pigmented inks actuator with constant maybe infeasible, polysilicon heater insulation in as pigment and 15 mWpower ULSI particles may jam input can provide Very low power the bendactuator 180 μN force and 10 consumption μm deflection. Many ink typesActuator motions can be used include: Simple planar Bend fabricationPush Small chip area Buckle required for Rotate each actuator Fastoperation High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conduct- Apolymer with a High force can Requires special IJ24 ive high coefficientof be generated materials polymer thermal expansion Very low powerdevelopment thermo- (such as PTFE) is consumption (High CTh elasticdoped with Many ink types conductive actuator conducting can be usedpolymer) substances to Simple planar Requires a PTFE increase itsfabrication deposition conductivity to Small chip area process, which isabout 3 orders of required for not yet standard in magnitude below eachactuator ULSI fabs that of copper. The Fast operation PTFE depositionconducting polymer High efficiency cannot be expands when CMOS followedwith resistively heated. compatible high temperature Examples ofvoltages and currents (above 350° C.) conducting dopants Easy extensionprocessing include: from single Evaporation and Carbon nanotubes nozzlesto CVD deposition Metal fibers pagewidth print techniques cannotConductive heads be used polymers such as Pigmented inks doped may beinfeasibie, polythiophene as pigment Carbon granules particles may jamthe bend actuator Shape A shape memory High force is Fatigue limits IJ26memory alloy such as TiNi available maximum number alloy (also known as(stresses of of cycles Nitinol - Nickel hundreds of Low strain (1%) isTitanium ailoy MPa) required to extend developed at the Large strain isfatigue resistance Naval Ordnance available (more Cycle rate limitedLaboratory) is than 3%) by heat removal thermally switched Highcorrosion Requires unusual between its weak resistance materials (TiNi)martensitic state and Simple The latent heat of its high stiffnessconstruction transformation austenic state. The Easy extension must beprovided shape of the actuator from single High current in itsmartensitic nozzles to operation state is deformed pagewidth printRequires pre- relative to the heads stressing to distort austenic shape.The Low voltage the martensitic shape change causes operation stateejection of a drop. Linear Linear magnetic Linear Magnetic Requiresunusual IJ12 Magnetic actuators include the actuators can hesemiconductor Actuator Linear Induction constructed with materials suchas Actuator (LIA), high thrust, long soft magnetic Linear Permanenttravel, and high alloys (e.g. Magnet efficiency using CoNiFe)Synchronous planar Some varieties Actuator (LPMSA), semiconductor alsorequire Linear Reluctance fabrication permanent Synchronous techniquesmagnetic Actuator (LRSA), Long actuator materials such as LinearSwitched travel is Neodymium iron Reluctance Actuator available boron(NdFeB) (LSRA), and the Medium force is Requires complex Linear Stepperavailable multi-phase drive Actuator (LSA). Low voltage circuitryoperation High current operation Basic operation mode Actuator This isthe simplest Simple Drop repetition Thermal ink jet directly mode ofoperation: operation rate is usually Piezoelectric ink jet pushes inkthe actuator directly No external limited to around IJ01. IJ02, IJ03,supplies sufficient fields required 10 kHz. IJ04, IJ05, IJ06, kineticenergy to Satellite drops However, this is IJ07, IJ09, IJ11, expel thedrop. The can be avoided not fundamental IJ12, IJ14, IJ16, drop musthave a if drop velocity to the method, IJ20, IJ22, IJ23, sufficientvelocity to is less than 4 but is related to IJ24, IJ25, IJ26, overcomethe m/s the refill method IJ27, IJ28, IJ29, surface tension. Can beefficient, normally used IJ30, IJ31, IJ32, depending upon All of thedrop IJ33, IJ34, IJ35, the actuator kinetic energy IJ36, IJ37, IJ38,used must be provided IJ39, IJ40, IJ41, by the actuator IJ42, IJ43, IJ44Satellite drops usually form if drop velocity is greater than 4.5 m/sProximity The drops to be Very simple Requires close Silverbrook, EP0771 658 A2 printed are selected print head proximity and related bysome manner fabrication can between the print patent applications (e.g.thermally be used head and the induced surface The drop print media ortension reduction of selection means transfer roller pressurized ink).does not need to May require two Selected drops are provide the printheads separated from the energy required printing alternate ink in thenozzle by to separate the rows of the contact with the drop from theimage print medium or a nozzle Monolithic color transfer roller. printheads are difficult Electro- The drops to be Very simple Requires verySilverbrook, EP 0771 658 A2 static pull printed are selected print headhigh electrostatic and related on ink by some manner fabrication canfield patent applications (e.g. thermally be used Electrostatic fieldTone-Jet induced surface The drop for small nozzle tension reduction ofselection means sizes is above air pressurized ink). does not need tobreakdown Selected drops are provide the Electrostatic field separatedfrom the energy required may attract dust ink in the nozzle by toseparate the a strong electric drop from the field. nozzle Magnetic Thedrops to be Very simpie Requires Silverbrook, EP 0771 658 A2 pull on inkprinted are selected print head magnetic ink and related by some mannerfabrication can Ink colors other patent applications (e.g. thermally beused than black are induced surface The drop difficult tension reductionof selection means Requires very pressurized ink). does not need to highmagnetic Selected drops are provide the fields separated from the energyrequired ink in the nozzle by to separate the a strong magnetic dropfrom the field acting on the nozzle magnetic ink. Shutter The actuatormoves High speed Moving parts are IJ13, IJ17, IJ21 a shutter to block(>50 kHz) required ink flow to the operation can be Requires ink nozzle.The ink achieved due to pressure pressure is pulsed at reduced refillmodulator a multiple of the time Friction and wear drop ejection Droptiming can must be frequency. be very accurate considered The actuatorStiction is energy can be possible very low Shuttered The actuator movesActuators with Moving parts are IJ08, IJ15, IJ18, grill a shutter toblock small travel can required IJ19 ink flow through a be used Requiresink grill to the nozzle. Actuators with pressure The shutter small forcecan modulator movement need be used Friction and wear only be equal tothe High speed must be width of the grill (>50 kHz) considered holes.operation can be Stiction is achieved possible Pulsed A pulsed magneticExtremely low Requires an IJ10 magnetic field attracts an ‘ink energyexternal pulsed pull on ink pusher’ at the drop operation is magneticfield pusher ejection frequency. possible Requires special An actuatorcontrols No heat materials for both a catch, which dissipation theactuator and prevents the ink problems the ink pusher pusher from movingComplex when a drop is not construction to be ejected. Auxiliarymechanism (applied to all nozzles) None The actuator directly Simplicityof Drop ejection Most ink jets, including fires the ink drop,construction energy must be piezoelectric and thermal and there is noSimplicity of supplied by bubble. external field or operation individualnozzle IJ01, IJ02, IJ03, other mechanism Small physical actuator IJ04,IJ05, IJ07, required. size IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23,IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35,IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP 0771 658 A2ink oscillates, providing pressure can ink pressure and related pressuremuch of the drop provide a refill osciilator patent applications(including ejection energy. The pulse, allowing Ink pressure IJ08, IJ13,IJ15, acoustic actuator selects higher operating phase and IJ17, IJ18,IJ19, stimu- which drops are to speed amplitude must IJ21 lation) befired by The actuators be carefully selectively blocking may operatecontrolled or enabling nozzles. with much Acoustic The ink pressurelower energy reflections in the oscillation may be Acoustic lenses inkchamber achieved by can be used to must be designed vibrating the printfocus the sound for head, or preferably on the nozzles by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP 0771 658 A2 proximity placed in close High accuracy assembly andrelated proximity to the Simple print required patent applications printmedium. head Paper fibers may Selected drops construction cause problemsprotrude from the Cannot print on print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to High accuracy Bulky Silverbrook, EP 0771 658 A2 roller atransfer roller Wide range of Expensive and related instead of straightto print substrates Complex patent applications the print medium. A canbe used construction Tektronix hot melt transfer roller can Ink can bedried piezoelectric ink jet also be used for on the transfer Any of theIJ series proximity drop roller separation. Electro- An electric fieldis Low power Field strength Silverbrook, EP 0771 658 A2 static used toaccelerate Simple pnnt required for and related selected drops headseparation of patent applications towards the print construction smalldrops is Tone-Jet medium. near or above air breakdown Direct A magneticfield is Low power Requires Silverbrook, EP 0771 658 A2 magnetic used toaccelerate Simple print magnetic ink and related field selected drops ofhead Requires strong patent applications magnetic ink constructionmagnetic field towards the print medium. Cross The print head is Doesnot Requires external IJ06, IJ16 magnetic placed in a constant requiremagnet field magnetic field. The magnetic Current densities Lorenz forcein a materials to be may be high, current carrying integrated in theresulting in wire is used to move print head electromigration theactuator. manufacturing problems process Pulsed A pulsed magnetic Verylow power Complex print IJ10 magnetic field is used to operation is headconstruction field cyclically attract a possible Magnetic paddle, whichSmall print head materials pushes on the ink. A size required in printsmall actuator head moves a catch, which selectively prevents the paddlefrom moving. Actuator amplification or modification method None Noactuator Operational Many actuator Thermal Bubble Ink jet mechanicalsimplicity mechanisms IJ01, IJ02, IJ06, amplification is have IJ07,IJ16, IJ25, IJ26 used. The actuator insufficient directly drives thetravel, or drop ejection insufficient process. force, to efficientlydrive the drop ejection process Differential An actuator materialProvides greater High stresses Piezoelectric expansion expands more ontravel in a are involved IJ03, IJ09, IJ17, bend one side than on thereduced print Care must be IJ18, IJ19, IJ20, actuator other. The headarea taken that the IJ21, IJ22, IJ23, expansion may be materials do notIJ24, IJ27, IJ29, thermal, delaminate IJ30, IJ31, IJ32, piezoelectric,Residual bend IJ33, IJ34, IJ35, magnetostrictive, or resulting fromIJ36, IJ37, IJ38, other mechanism. high IJ39, IJ42, IJ43, The bendactuator temperature or IJ44 converts a high high stress force lowtravel during actuator mechanism formation to high travel, lower forcemechanism. Transient A trilayer bend Very good High stresses IJ40, IJ41bend actuator where the temperature are involved actuator two outsidelayers stability Care must be are identical. This High speed, as a takenthat the cancels bend due to new drop can be materials do not ambienttemperature fired before heat delaminate and residual stress. dissipatesThe actuator only Cancels residual responds to transient stress ofheating of one side formation or the other. Reverse The actuator loads aBetter coupling Fabrication IJ05, IJ11 spring spring. When the to theink complexity actuator is turned High stress in off, the spring thespring releases. This can reverse the force/distance curve of theactuator to make it compatible with the force/time requirements of thedrop ejection. Actuator A series of thin Increased travel Increased Somepiezoelectric ink stack actuators are Reduced drive fabrication jetsstacked. This can be voltage complexity IJ04 appropriate where Increasedactuators require possibility of high electric field short circuitsstrength, such as due to pinholes electrostatic and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available may not addIJ20, IJ22, IJ28, simultaneously to from an actuator linearly, IJ42,IJ43 move the ink. Each Multiple reducing actuator need actuators can beefficiency provide only a positioned to portion of the force control inkflow required. accurately Linear A linear spring is Matches low Requiresprint IJ15 Spring used to transform a travel actuator head area formotion with small with higher the spring travel and high force travelinto a longer travel, requirements lower force motion. Non-contactmethod of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to IJ35 greater travel in a area planar reduced chiparea. Planar implementations implementations due to extreme arerelatively fabrication easy to difficulty in fabricate. otherorientations. Flexure A bend actuator has Simple means Care must beIJ10, IJ19, IJ33 bend a small region near of increasing taken not toactuator the fixture point, travel of a bend exceed the which flexesmuch actuator elastic limit in more readily than the flexure area theremainder of the Stress actuator. The distribution is actuator flexingis very uneven effectively Difficult to converted from an accuratelyeven coiling to an model with angular bend, finite element resulting ingreater analysis travel of the actuator tip. Catch The actuator Very lowComplex IJ10 controls a small actuator energy construction catch. Thecatch Very small Requires either enables or actuator size external forcedisables movement Unsuitable for of an ink pusher that pigmented inks iscontrolled in a bulk manner. Gears Gears can be used to Low force, lowMoving parts IJ13 increase travel at the travel actuators are requiredexpense of duration. can he used Several actuator Circular gears, rackCan be cycles are and pinion, ratchets, fabricated using required andother gearing standard surface More complex methods can be MEMS driveelectronics used. processes Complex constrtiction Friction, friction,and wear are possible Buckle A buckle plate can Very fast Must stay S.Hirata et al, “An Ink-jet plate be used to change a movement withinelastic Head Using Diaphragm slow actuator into a achievable limits ofthe Microactuator”, Proc. fast motion. It can materials for IEEE MEMS,Feb. 1996, also convert a high long device life pp 418-423. force, lowtravel High stresses IJ18, IJ27 actuator into a high involved travel,medium force Generally high motion. power requirement Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance of force. curveLever A lever and fulcrum Matches low High stress IJ32, IJ36, IJ37 isused to transform travel actuator around the a motion with small withhigher fulcrum travel and high force travel into a motion withrequirements longer travel and Fulcrum area lower force. The has nolinear lever can also movement, and reverse the direction can be usedfor of travel. a fluid seal Rotary The actuator is High Complex IJ28impeller connected to a mechanical construction rotary impeller. Aadvantage Unsuitable for small angular The ratio of pigmented inksdeflection of the force to travel actuator results in a of the actuatorrotation of the can be matched impeller vanes, to the nozzle which pushthe ink requirements by against stationary varying the vanes and out ofthe number of nozzle. impeller vanes Acoustic A refractive or No movingLarge area 1993 Hadimioglu et al, lens diffractive (e.g. zone partsrequired EUP 550,192 plate) acoustic lens Only relevant 1993 Elrod etal, EUP is used to for acoustic ink 572,220 concentrate sound jetswaves. Sharp A sharp point is Simple Difficult to Tone-jet conductiveused to concentrate construction fabricate using point an electrostaticfield. standard VLSI processes for a surface ejecting ink-jet Onlyrelevant for electrostatic ink jets Actuator motion Volume The volume ofthe Simple High energy is Hewlett-Packard Thermal expansion actuatorchanges, construction in typically Ink jet pushing the ink in the caseof required to Canon Bubblejet all directions. thermal ink jet achievevolume expansion. This leads to thermal stress, cavitation, and kogationin thermal ink jet implementations Linear, The actuator moves EfficientHigh fabrication IJ01, IJ02, IJ04, normal to in a direction normalcoupling to ink complexity may IJ07, IJ11, IJ14 chip to the print headdrops ejected be required to surface surface. The nozzle normal to theachieve is typically in the surface perpendicular line of movement.motion Parallel to The actuator moves Suitable for Fabrication IJ12,IJ13, IJ15, chip parallel to the print planar complexity IJ33, IJ34,IJ35, surface head surface. Drop fabrication Friction IJ36 ejection maystill be Stiction normal to the surface. Membrane An actuator with a Theeffective Fabrication 1982 Howkins U.S. Pat. No. push high force butsmall area of the complexity 4,459,601 area is used to push actuatorActuator size a stiff membrane becomes the Difficulty of that is incontact membrane area integration in a with the ink. VLSI process RotaryThe actuator causes Rotary levers Device IJ05, IJ08, IJ13, the rotationof some may be used to complexity IJ28 element, such a grill increasetravel May have or impeller Small chip area friction at a requirementspivot point Bend The actuator bends A very small Requires the 1970 Kyseret al U.S. Pat. No. when energized. change in actuator to be 3,946,398This may be due to dimensions can made from at 1973 Stemme U.S. Pat. No.differential thermal be converted to least two 3,747,120 expansion, alarge motion. distinct layers, IJ03, IJ09, IJ10, piezoelectric or tohave a IJ19, IJ23, IJ24, expansion, thermal IJ25, IJ29, IJ30,magnetostriction, or difference IJ31, IJ33, IJ34, other form of acrossthe IJ35 relative dimensional actuator change. Swivel The actuatorswivels Allows Inefficient IJ06 around a central operation wherecoupling to the pivot. This motion is the net linear ink motion suitablewhere there force on the are opposite forces paddle is zero applied toopposite Small chip area sides of the paddle, requirements e.g. Lorenzforce. Straighten The actuator is Can be used Requires careful IJ26,IJ32 normally bent, and with shape balance of straightens when memoryalloys stresses to energized. where the ensure that the austenic phasequiescent bend is planar is accurate Double The actuator bends Oneactuator Difficult to IJ36, IJ37, IJ38 bend in one direction can be usedto make the drops when one element is power two ejected by bothenergized, and nozzles. bend directions bends the other way Reduced chipidentical. when another size. A small element is Not sensitive toefficiency loss energized. ambient compared to temperature equivalentsingle bend actuators. Shear Energizing the Can increase the Not readily1985 Fishbeck U.S. Pat. No. actuator causes a effective travelapplicable to 4,584,590 shear motion in the of piezoelectric otheractuator actuator material. actuators mechanisms Radial The actuatorRelatively easy High force 1970 Zoltan U.S. Pat. No. con- squeezes anink to fabricate required 3,683,212 striction reservoir, forcing singlenozzles Inefficient ink from a from glass Difficult to constrictednozzle. tubing as integrate with macroscopic VLSI processes stracturesCoil/ A coiled actuator Easy to Difficult to IJ17, IJ21, IJ34, uncoiluncoils or coils fabricate as a fabricate for IJ35 more tightly. Theplanar VLSI non-planar motion of the free process devices end of theactuator Small area Poor out-of- ejects the ink. required, planestiffness therefore low cost Bow The actuator bows Can increase theMaximum IJ16, IJ18, IJ27 (or buckles) in the speed of travel travel ismiddle when Mechanically constrained energized. rigid High forcerequired Push-Pull Two actuators The structure is Not readily IJ18control a shutter. pinned at both suitable for ink One actuator pullsends, so has a jets which the shutter, and the high out-of- directlypush other pushes it. plane rigidity the ink Curl A set of actuatorsGood fluid flow Design IJ20, IJ42 inwards curl inwards to to the regioncomplexity reduce the volume behind the of ink that they actuatorenclose. increases efficiency Curl A set of actuators RelativelyRelatively large IJ43 outwards curl outwards, simple chip areapressurizing ink in a construction chamber surrounding the actuators,and expelling ink from a nozzle in the chamber. Iris Multiple vanes Highefficiency High fabrication IJ22 enclose a volume of Small chip areacomplexity ink. These Not suitable for simultaneously pigmented inksrotate, reducing the volume between the vanes. Acoustic The actuator Theactuator Large area 1993 Hadimioglu et al, vibration vibrates at a highcan be required for EUP 550,192 frequency physically efficient 1993Elrod et al, EUP distant from the operation at 572,220 ink usefulfrequencies Acoustic coupling and crosstalk Complex drive circuitry Poorcontrol of drop volume and position None In various ink jet No movingVarious other Silverbrook, EP 0771 658 A2 designs the actuator partstradeoffs are and related patent does not move. required to applicationseliminate Tone-jet moving parts Nozzle refill method Surface This is thenormal Fabrication Low speed Thermal ink jet tension way that inkjetsare simplicity Surface tension Piezoelectric ink jet refilled. After theOperational force relatively IJ01-IJ07, IJ10- actuator is energized,simplicity small IJ14, IJ16, IJ20, it typically returns compared toIJ22-IJ45 rapidly to its normal actuator force position. This rapid Longrefill return sucks in air time usually through the nozzle dominates theopening. The ink total repetition surface tension at the rate nozzlethen exerts a small force restoring the meniscus to a minimum area. Thisforce refills the nozzle. Shuttered Ink to the nozzle High speedRequires IJ08, IJ13, IJ15, oscillating chamber is provided Low actuatorcommon ink IJ17, IJ18, IJ19, ink at a pressure that energy, as thepressure IJ21 pressure oscillates at twice the actuator need oscillatordrop ejection only open or May not be frequency. When a close thesuitable for drop is to be ejected, shutter, instead pigmented inks theshutter is opened of ejecting the for 3 half cycles: ink drop dropejection, actuator return, and refill. The shutter is then closed toprevent the nozzle chamber emptying during the Refill After the mainHigh speed, as Requires two IJ09 actuator actuator has ejected a thenozzle is independent drop a second (refill) actively actuators peractuator is energized. refilled nozzle The refill actuator pushes inkinto the nozzle chamber. The refill actuator returns slowly, to preventits return from emptying the chamber again. Positive The ink is held aHigh refill rate, Surface spill Silverbrook, EP 0771 658 A2 ink slightpositive therefore a must be and related patent pressure pressure. Afterthe high drop prevented applications ink drop is ejected, repetitionrate Highly Alternative for: the nozzle chamber is possible hydrophobicIJ01-IJ07, IJ10-IJ14, fllls quickly as print head IJ16, IJ20, IJ22-IJ45surface tension and surfaces are ink pressure both required operate torefill the nozzle. Method of restricting back-flow through inlet Longinlet The ink inlet Design Restricts refill Thermal ink jet channelchannel to the simplicity rate Piezoelectric ink jet nozzle chamber isOperational May result in a IJ42, IJ43 made long and simplicityrelatively large relatively narrow, Reduces chip area relying on viscouscrosstalk Only partially drag to reduce inlet effective back-flow.Positive The ink is under a Drop selection Requires a Silverbrook, EP0771 658 A2 ink positive pressure, so and separation method (such andrelated patent pressure that in the quiescent forces can be as a nozzlerim applications state some of the ink reduced or effective Possibleoperation of the drop already Fast refill time hydrophobizing,following: protrudes from the or both) to IJ01-IJ07, IJ09-IJ12, nozzle.prevent IJ14, IJ16, IJ20, This reduces the flooding of the IJ22,IJ23-IJ34, pressure in the ejection IJ36-IJ41, IJ44 nozzle chambersurface of the which is required to print head. eject a certain volumeof ink. The reduction in chamber pressure results in a reduction in inkpushed out through the inlet. Baffle One or more baffles The refill rateis Design HP Thermal Ink Jet are placed in the not as restrictedcomplexity Tektronix piezoelectric ink inlet ink flow. When as the longinlet May increase jet the actuator is method. fabrication energized,the rapid Reduces complexity ink movement crosstalk (e.g. Tektronixcreates eddies which hot melt restrict the flow Piezoelectric throughthe inlet. print heads). The slower refill process is unrestricted, anddoes not result in eddies. Flexible In this method Significantly Notapplicable Canon flap recently disclosed reduces back- to most ink jetrestricts by Canon, the flow for edge- configurations inlet expandingactuator shooter thermal Increased (bubble) pushes on a ink jet devicesfabrication flexible flap that complexity restricts the inlet. Inelasticdeformation of polymer flap results in creep over extended use Inletfilter A filter is located Additional Restricts refill IJ04, IJ12, IJ24,between the ink inlet advantage of rate IJ27, IJ29, IJ30 and the nozzleink filtration May result in chamber. The filter Ink filter may complexhas a multitude of be fabricated construction small holes or slots, withno restricting ink flow. additional The filter also process stepsremoves particles which may block the nozzle. Small inlet The ink inletDesign Restricts refill IJ02, IJ37, IJ44 compared channel to thesimplicity rate to nozzle nozzle chamber has May result in a asubstantially relatively large smaller cross section chip area than thatof the Only partially nozzle, resulting in effective easier ink egressout of the nozzle than out of the inlet. Inlet A secondary Increasesspeed Requires IJ09 shutter actuator controls the of the ink jetseparate refill position of a shutter, print head actuator and closingoff the ink operation drive circuit inlet when the main actuator isenergized. The inlet The method avoids Back-flow Requires IJ01, IJ03,IJ05, is located the problem of inlet problem is careful design IJ06,IJ07. IJ10, behind the back-flow by eliminated to minimize IJ11, IJ14,IJ16, ink- arranging the ink- the negative IJ22, IJ23, IJ25, pushingpushing surface of pressure IJ28, IJ31, IJ32, surtace the actuatorbetween behind the IJ33, IJ34, IJ35, the inlet and the paddle IJ36,IJ39, IJ40, nozzle. IJ41 Part of the The actuator and a SignificantSmall increase IJ07, IJ20, IJ26, actuator wall of the ink reductions inin fabrication IJ38 moves to chamber are back-flow can complexity shutoff arranged so that the be achieved the inlet motion of the Compactactuator closes off designs possible the inlet. Nozzle In some Inkback-flow None related to Silverbrook, EP 0771 658 A2 actuatorconfigurations of problem is ink back-flow and related patent does notink jet, there is no eliminated on actuation applications result inexpansion or Valve-jet ink back- movement of an Tone-jet flow actuatorwhich may cause ink back-flow through the inlet. Nozzle clearing methodNormal All of the nozzles No added May not be Most ink jet systemsnozzle are fired complexity on sufficient to IJ01, IJ02, IJ03, firingperiodically, before the print head displace dried IJ04, IJ05, IJ06, theink has a chance ink IJ07, IJ09, IJ10, to dry. When not in IJ11, IJ12,IJ14, use the nozzles are IJ16, IJ20, IJ22, sealed (capped) IJ23, IJ24,IJ25, against air. IJ26, IJ27, IJ28, The nozzle firing is IJ29, IJ30,IJ31, usually performed IJ32, IJ33, IJ34, during a special IJ36, IJ37,IJ38, clearing cycle, after IJ39, IJ40, IJ41, first moving the IJ42,IJ43, IJ44, print head to a IJ45 cleaning station. Extra In systemswhich Can be highly Requires Silverbrook, EP 0771 658 A2 power to heatthe ink, but do effective if the higher drive and related patent inkheater not boil it under heater is voltage for applications normalsituations, adjacent to the clearing nozzle clearing can nozzle Mayrequire be achieved by over- larger drive powering the heatertransistors and boiling ink at the nozzle. Rapid The actuator is firedDoes not Effectiveness May be used with: success- in rapid succession.require extra depends IJ01, IJ02, IJ03, ion of In some drive circuits onsubstantially IJ04, IJ05, IJ06, actuator configurations, this the printhead upon the IJ07, IJ09, IJ10, pulses may cause heat Can be readilyconfiguration IJ11, IJ14, IJ16, build-up at the controlled and of theinkjet IJ20, IJ22, IJ23, nozzle which boils initiated by nozzle IJ24,IJ25, IJ27, the ink, clearing the digital logic IJ28, IJ29, IJ30,nozzle. In other IJ31, IJ32, IJ33, situations, it may IJ34, IJ36, IJ37,cause sufficient IJ38, IJ39, IJ40, vibrations to IJ41, IJ42, IJ43,dislodge clogged IJ44, IJ45 nozzles. Extra Where an actuator is A simpleNot suitable May be used with: power to not normally driven solutionwhere where there is IJ03, IJ09, IJ16, ink to the limit of itsapplicable a hard limit to IJ20, IJ23, IJ24, pushing motion, nozzleactuator IJ25, IJ27, IJ29, actuator clearing may be movement IJ30, IJ31,IJ32, assisted by IJ39, IJ40, IJ41, providing an IJ42, IJ43, IJ44,enhanced drive IJ45 signal to the actuator. Acoustic An ultrasonic waveA high nozzle High IJ08, IJ13, IJ15, resonance is applied to the inkclearing implementation IJ17, IJ18, IJ19, chamber. This wave capabilitycan cost if IJ21 is of an appropriate he achieved system does amptitudeand May be not already frequency to cause implemented at include ansufficient force at very low cost in acoustic the nozzle to clearsystems which actuator blockages. This is already include easiest toachieve if acoustic the ultrasonic wave actuator is at a resonantfrequency of the ink cavity. Nozzle A microfabricated Can clear AccurateSilverbrook, EP 0771 658 A2 clearing plate is pushed severely mechanicaland related patent plate against the nozzles. clogged nozzles alignmentis applications The plate has a post required for every nozzle. A Movingparts post moves through are required each nozzle, There is risk ofdisplacing dried ink. damage to the nozzles Accurate fabrication isrequired Ink The pressure of the May be Requires May be used with all IJpressure ink is temporarily effective where pressure pump series inkjets pulse increased so that ink other methods or other streams from allof cannot be used pressure the nozzles. This actuator may be used inExpensive conjunction with Wasteful of actuator energizing. ink Printhead A flexible ‘blade’ is Effective for Difficult to use Many ink jetsystems wiper wiped across the planar print if print head print headsurface. head surfaces surface is non- The blade is usually Low costplanar or very fabricated from a fragile flexible polymer, Requires e.g.rubber or mechanical synthetic elastomer. parts Blade can wear out inhigh volume print systems Separate A separate heater is Can be effectiveFabrication Can be used with many IJ ink boiling provided at the whereother complexity series ink jets heater nozzle although the nozzleclearing normal drop e- methods cannot ection mechanism be used does notrequire it. Can be The heaters do not implemented at require individualno additional drive circuits, as cost in some ink many nozzles can bejet cleared configuration simultaneously, and no imaging is required.Nozzle plate construction Electro- A nozzle plate is Fabrication HighHewlett Packard Thermal formed separately fabricated simplicitytemperatures Ink jet nickel from electroformed and pressures nickel, andbonded are required to to the print head bond nozzle chip. plate Minimumthickness constraints Differential thermal expansion Laser Individualnozzle No masks Each hole must Canon Bubblejet ablated or holes areablated by required be individually 1988 Sercel et al., SPIE, drilled anintense UV laser Can be quite formed Vol. 998 Excimer Beam polymer in anozzle plate, fast Special Applications, pp. 76-83 which is typically aSome control equipment 1993 Watanabe et al., polymer such as over nozzlerequired U.S. Pat. No. 5,208,604 polyimide or profile is Slow wherepolysulphone possible there are many Equipment thousands of required isnozzles per relatively low print head cost May produce thin burrs atexit holes Silicon A separate nozzle High accuracy Two part K. Bean,IEEE micro- plate is is attainable construction Transactions on Electronmachined micromachined High cost Devices, Vol. ED-25, No. from singlecrystal Requires 10, 1978, pp 1185-1195 silicon, and bonded precisionXerox 1990 Hawkins et al., to the print head alignment U.S. Pat. No.4,899,191 wafer. Nozzles may be clogged by adhesive Glass Fine glass Noexpensive Very small 1970 Zoltan U.S. Pat. No. capillaries capillariesare drawn equipment nozzle sizes 3,683,212 from glass tubing. requiredare difficult to This method has Simple to make form been used forsingle nozzles Not suited for making individual mass nozzles, but isproduction difficult to use for bulk manufacturing of print heads withthousands of nozzles. Monolithic, The nozzle plate is High accuracyRequires Silverbrook, EP 0771 658 A2 surface deposited as a layer (<1μm) sacrificial layer and related patent micro- using standard VLSIMonolitnic under the applications machined deposition Low cost nozzleplate to IJ01, IJ02, IJ04, using VLSI techniques. Nozzles Existing formthe IJ11, IJ12, IJ17, litho- are etched in the processes can nozzleIJ18, IJ20, IJ22, graphic nozzle plate using be used chamber IJ24, IJ27,IJ28, processes VLSI lithography Surface may IJ29, IJ30, IJ31, andetching. be fragile to IJ32, IJ33, IJ34, the touch IJ36, IJ37, IJ38,IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is aHigh accuracy Requires long IJ03, IJ05, IJ06, etched buried etch stop in(<1 μm) etch times IJ07, IJ08, IJ09, through the wafer. NozzleMonolithic Requires a IJ10, IJ13, IJ14, substrate chambers are etchedLow cost support wafer IJ15, IJ16, IJ19, in the front of the Nodifferential IJ21, IJ23, IJ25, wafer, and the wafer expansion IJ26 isthinned from the back side. Nozzles are then etched in the etch stoplayer. No nozzle Various methods No nozzles to Difficult to Ricoh 1995Sekiya et al plate have been tried to become clogged control drop U.S.Pat. No. 5,412,413 eliminate the position 1993 Hadimioglu et al EUPnozzles entirely, to accurately 550,192 prevent nozzle Crosstalk 1993Elrod et al EUP clogging. These problems 572,220 include thermal bubblemechanisms and acoustic lens mechanisms Trough Each drop ejector ReducedDrop flring IJ35 has a trough through manufacturing direction is which apaddle complexity sensitive to moves. There is no Monolithic wicking.nozzle plate. Nozzle slit The elimination of No nozzles to Difficult to1989 Saito et al instead of nozzle holes and become clogged control dropU.S. Pat. No. 4,799,068 individual replacement by a slit positionnozzles encompassing many accurately actuator positions Crosstalkreduces nozzle problems clogging, but increases crosstalk due to inksurface waves Drop ejection direction Edge Ink flow is along the SimpleNozzles Canon Bubblejet 1979 (‘edge surface of the chip, constructionlimited to edge Endo et al GB patent shooter’) and ink drops are Nosilicon High 2,007,162 ejected from the etching required resolution isXerox heater-in-pit 1990 chip edge. Good heat difficult Hawkins et alU.S. Pat. No. sinking via Fast color 4,899,181 substrate printingTone-jet Mechanically requires one strong print head per Ease of chipcolor handing Surface Ink flow is along the No bulk silicon Maximum inkHewlett-Packard TIJ 1982 (‘roof surface of the chip, etching requiredflow is Vaught et al U.S. Pat. No. shooter’) and ink drops are Siliconcan severely 4,490,728 ejected from. the make an restricted IJ02, IJ11,IJ12, chip surface, normal effective heat IJ20, IJ22 to the plane of thesink chip. Mechanical strength Through Ink flow is through. High inkflow Requires bulk Silverbrook, EP 0771 658 A2 chip, the chip, and inkSuitable for silicon etching and related patent forward drops areejected pagewidth print applications (‘up from the front heads IJ04,IJ17, IJ18, shooter’) surface of the chip. High nozzle IJ24, IJ27-IJ45packing density therfore low manufacturing Through Ink flow is throughHigh ink flow Requires wafer IJ01, IJ03, IJ05, chip, the chip, and inkSuitable for thinning IJ06, IJ07, IJ08, reverse drops are ejectedpagewidth print Requires IJ09, IJ10, IJ13, (‘down from the rear surfaceheads special IJ14, IJ15, IJ16, shooter’) of the chip. High nozzlehandling IJ19, IJ21, IJ23, packing density during IJ25, IJ26 thereforelow manufacture manufacturing cost Through Inkflow is through Suitablefor Pagewidth Epson Stylus actuator the actuator, which piezoelectricprint heads Tektronix hot melt is not fabricated as print heads requireseveral piezoelectric ink jets part of the same thousand substrate asthe connections to drive transistors. drive circuits Cannot bemanufactured in standard CMOS fabs Complex assembly required Ink typeAqueous, Water based ink Environmentally Slow drying Most existinginkjets dye which typically friendly Corrosive All IJ series ink jetscontains: water, dye, No odor Bleeds on Silverbrook, EP 0771 658 A2surfactant, paper and related patent applications humectant, and Maybiocide strikethrough Modern ink dyes Cockles paper have high water-fastness, light fastness Aqueous, Water based ink Environmentally Slowdrying IJ02, IJ04, IJ21, pigment which typically friendly CorrosiveIJ26, IJ27, IJ30 contains: water, No odor Pigment may Silverbrook, EP0771 658 A2 pigment, surfactant, Reduced bleed clog nozzles and relatedpatent humectant, and Reduced Pigment may applications biocide. wickingclog actuator Piezoelectric ink-jets Pigments have an Reduced mechanismsThermal ink jets (with advantage in reduced strikethrough Cockles papersignificant restrictions) bleed, wicking and strikethrough. Methyl MEKis a highly Very fast Odorous All IJ series ink jets Ethyl volatilesolvent used drying Flammable Ketone for industrial printing Prints on(MEK) on difficult surfaces various such as aluminum substrates suchcans. as metals and plastics Alcohol Alcohol based inks Fast dryingSlight odor All IJ series ink jets (ethanol, can be used where Operatesat Flammable 2-butanol, the printer must sub-freezing and operate attemperatures others) temperatures below Reduced paper the freezing pointof cockle water. An example of Low cost this is in-camera consumerphotographic printing. Phase The ink is solid at No drying Highviscosity Tektronix hot melt change room temperature, time-ink Printedink piezoelectric ink jets (hot melt) and is melted in the instantlytypically has a 1989 Nowak U.S. Pat. No. print head before freezes onthe ‘waxy’ feel 4,820,346 jetting. Hot melt inks print medium Printedpages All IJ series ink jets are usually wax Almost any may ‘block’based, with a melting print medium Ink point around 80° C. can be usedtemperature After jetting the ink No paper may be above freezes almostcockie occurs the curie point instantly upon No wicking of permanentcontacting the print occurs magnets medium or a transfer No bleed Inkheaters roller. occurs consume No power strikethrough Long warm-upoccurs time Oil Oil based inks are High solubility High viscosity: AllIJ series ink jets extensively used in medium for this is a offsetprinting. They some dyes significant have advantages in Does notlimitation for improved cockle paper use in ink jets, characteristics onDoes not wick which usually paper (especially no through paper require alow wicking or cockle). viscosity. Oil soluble dies and Some shortpigments are chain and required. multi-branched oils have a sufficientlylow viscosity. Slow drying Micro- A microemulsion is a Stops ink bleedViscosity All IJ series ink jets emulsion stable, self forming High dyehigher than emulsion of Oil, solubility water water, and surfactant.Water, oil, and Cost is slightly The characteristic amphiphilic higherthan drop size is less than soluble dies water based 100 nm, and is canbe used ink determined by the Can stabilize High surfactant preferredcurvature of pigment concentration the surfactant. suspensions required(around 5%)

What is claimed is:
 1. An ink jet printhead comprising: a nozzle chamberhaving an ink ejection port in one wall of said chamber; an ink supplysource interconnected to said nozzle chamber; an electrostatic actuatorcomprising a first planar electrode formed within a bottom substrate ofthe nozzle chamber and a moveable second planar electrode arranged abovethe first planar electrode and having a corrugated border portion, saidsecond planar electrode being moveable to a pre-firing position adjacentto said first planar electrode, upon forming a potential differenceacross said electrodes, thereby causing said corrugated border portionof said second electrode to concertina, such that, upon reduction ofsaid potential difference, said corrugated border portion returns to isquiescent position, thereby causing the ejection of ink from said nozzlechamber.
 2. An ink jet printhead as claimed in claim 1 wherein betweensaid first planar electrode and said second planar electrode is an airgap interconnected to an external atmosphere at a side of said nozzlechamber such that air flows into and out of said gap upon movement ofsaid actuator.
 3. An ink jet printhead as claimed in claim 2 whereinsaid gap is formed by utilization of a sacrificial material layer whichis etched away to release said second planar electrode structure.
 4. Anink jet printhead as claimed in claim 1 wherein the electrodes havefacing surfaces that are coated with a material having a low coefficientof friction so as to reduce the possibilities of stiction.
 5. An ink jetprinthead as claimed in claim 4 wherein said material comprisessubstantially polytetrafluoroethylene.
 6. An ink jet printhead asclaimed in claim 1 wherein said second planar electrode includes a layerof stiffening material for maintaining the stiffness of said secondplanar electrode.
 7. An ink jet printhead as claimed in claim 6 whereinsaid stiffening material comprises substantially nitride.
 8. An ink jetprinthead comprising: a nozzle chamber having an ink ejection port inone wall of said chamber; an ink supply source interconnected to saidnozzle chamber; an electrostatic actuator to eject ink from said nozzlechamber via said ink ejection port, said electrostatic actuatorcomprising a first planar electrode formed within a bottom substrate ofthe nozzle chamber and a moveable second planar electrode arranged abovethe first planar electrode, said nozzle chamber and said electrostaticactuator being formed from depositing and etching of material on asingle monolithic wafer.
 9. An ink jet printhead as claimed in claim 8wherein an outer surface of said ink chamber includes a plurality ofetchant holes provided so as to allow a more rapid etching ofsacrificial layers during construction.
 10. An ink jet printheadcomprising: a nozzle chamber having an ink ejection port in one wall ofsaid chamber; an ink supply source interconnected to said nozzlechamber; an electrostatic actuator comprising a first planar electrodeformed within a bottom substrate of the nozzle chamber and a moveablesecond planar electrode arranged above the first planar electrode andhaving a corrugated border portion, said second planar electrode beingmoveable to a pre-firing position adjacent to said first planarelectrode, upon forming a potential difference across said electrodes,thereby causing said corrugated border portion of said second electrodeto concertina, such that, upon reduction of said potential difference,said corrugated border portion returns to is quiescent position, therebycausing the ejection of ink from said nozzle chamber, said nozzlechamber and said electrostatic actuator being formed from depositing andetching of material on a single monolithic wafer, and wherein betweensaid first planar electrode and said second planar electrode is an airgap interconnected to an external atmosphere at a side of said nozzlechamber such that air flows into and out of said gap upon movement ofsaid actuator, and wherein the electrodes have facing surfaces that arecoated with a material comprising substantially polytetrafluoroethylene,and wherein said second planar electrode includes a layer of stiffeningmaterial comprising substantially nitride.